As is well known in the art, hair fibers are composed of a unique protein called "keratin" which is distinguished by the fact that it contains a very significant amount of an amino acid (cysteine) which contains the element sulfur in addition to the elements nitrogen, oxygen, carbon and hydrogen. In the natural synthesis of hair, the element sulfur covalently links intra or inter polypeptide chains (K) through two sulfur atoms (S-S) to give keratin protein (K-S-S-K). Only by chemical action can this covalent linkage be broken.
Since these disulfide bonds are relatively strong bonds and are not affected by water, permanent results are obtained by altering the disulfide bonds through cleavage and recombination. In this way, a permanent configuration change of the hair is attained. However, chemical action is required in order for this disulfide linkage to be broken. In this regard, many prior art compositions have been developed for permanent waving or straightening of hair which treat the hair with chemical agents to break the disulfide (cysteine) linkage in the hair while the hair is mechanically maintained in the desired configuration.
When a sufficient number of hair disulfide bonds have been broken, the hair is realigned to pair previously unpaired hair protein thiol groups opposite each other. At this point, the hair is rinsed to remove the first chemical reactant and then saturated with a second agent to reform the disulfide bonds between the newly paired hair protein thiols. This gives the hair a new configuration.
Although the chemicals employed in achieving either hair straightening or permanent hair waving provide excellent results, process problems exist which are difficult to control. One of the disadvantages is the fact that these processes must be conducted at elevated pH levels. However, since the skin surface of humans is usually at a weak acidic level, the use of products at elevated pH causes discomfort, irritation, and/or adverse reactions. Although low pH levels would be desirable, the permanent wave or straightening results produced at low pH levels are not satisfactory. Other disadvantages of prior art chemical agents are the irreversible fiber alteration made evident by increased fiber porosity and decreased tensile properties.
In the art of chemically altering hair fiber configurations, there is much trial and error, with the hair being over processed, in some instances. The characteristics of over-processing are raspy feel to the hair or a loss of natural underlying color. Structural evaluation of the hair fiber by instrumentation usually reveals that the structural integrity of the hair is lessened, which is evidenced by either an increase in the amount of cysteine and cysteic acid or a lessening of the cysteine content relative to the hair not so processed.
In view of the substantial damage that may be caused to hair fibers by employing chemicals for structurally altering the hair fiber configuration, increased interest has been paid to the development of chemicals and application techniques which achieve a hair configuration altering result which is on a temporary basis and does not cause a chemical hair fiber interaction. Although substantial effort has been expended in the prior art to achieve an effective composition capable of producing hair straightening on a temporary basis without adversely affecting the hair fiber itself, such attempts have failed to produce a viable composition, prior to the present invention.